A hinge structure normally includes two hinge members which are rotatably secured together by a pin or the like. Automatically operated doors, such as those commonly used in shopping centers, schools, drugstores, or the like are continually operated and are substantially heavier and larger than those used in most homes. As will be understood, continual use of the door submits the hinge structure to extensive wear. Notwithstanding their continual use and the substantial load placed thereon, a hinge structure is expected to perform error free and with minimum maintenance.
Increases in height and/or weight of the door or the like carried by the hinge member, adds to the frictional sliding contact between the hinge members and thereby increases the wear on the hinge structure. As may be appreciated, and despite the wear on such hinge structures, the hinge members are not normally permitted to longitudinally move relative to each other during operation.
My U.S. Pat. No. 3,092,870, dated June 11, 1963, discloses a pinless hinge structure offering increased performance and durability. Such a hinge structure includes two longitudinally extending hinge members which are rotatably joined along adjacent longitudinal edges by intermeshing gear segments forming part of the hinge members. A clamp member maintains the gear segments in mesh relative to each other while permitting smooth and uniform movement of the hinge members through a full arc of travel of the hinge. The hinge structure can be formed from a wide variety of metals and plastic materials, and can be manufactured by extrusion, rolling, drawing, machining, molding, and other forming operations.
The design and performance of the hinge structure disclosed in the above-identified patent was further enhanced through the provision of a longitudinal thrust bearing which was the subject of my U.S. Pat. No. 3,402,422, dated Sept. 24, 1968. My patented longitudinal thrust bearing comprises a solid bearing member disposed in longitudinally co-extensive recesses formed in adjacent longitudinal edges of each rotatable hinge member. The longitudinal dimensions of the bearing member and the recesses in which the bearing member is disposed are such that upper and lower surfaces of the recesses slidably contact upper and lower bearing surfaces of the bearing member disposed therein whereby inhibiting longitudinal movement of one hinge member with respect to the other hinge member.
Preferably, several thrust bearings are longitudinally spaced along the length of the door to distribute their load bearing capability. Despite their improved performance, and because of the continual relative sliding engagement between its upper and lower surfaces, such thrust bearings do, on occasion, require replacement.
Replacement of any or all of the thrust bearings normally requires complete disassembly of the hinge structure from the associated door. As will be appreciated, repairs on a door leading to a commonly frequented building such as a school, hospital, or the like interrupt or limit accessibility to such a building. Even if only for a short time period, such interruptions to building access are undesirable and therefore, should be maintained to a minimum if not eliminated. As will be appreciated, the ability to replace the thrust bearing assembly without requiring disassembly of the hinge structure from the associated door would greatly reduce the time required to perform maintenance thereon, reduce maintenance costs, and reduce disruptions to store access.